This invention relates to demand ink jets, and more particularly, to the priming of demand ink jets.
A demand ink jet comprises an ink jet chamber including an orifice and an inlet. In order to ready such a jet for printing, it is necessary to prime the jet, i.e., be sure that the chamber is filled with ink so that changes in the state of energization of the transducer associated with the jet will result in the ejection of a droplet of ink from the orifice of the chamber. The changes in the state of energization of the transducer are on demand, i.e., whenever a droplet of ink is desired at a predetermined location.
Priming of an ink jet can present a substantial problem. In some instances, it is possible, during priming, for air to become trapped in a jet in a manner so as to prevent the proper filling of the chamber associated with the jet. These problems are compounded where a plurality or an array of jets are utilized since one jet may properly prime for a predetermined length of time while another jet will not. It is, of course, imperative in a demand ink jet that each jet in an array be primed for printing upon demand. Unlike a continuous ink jet system, an ink supply to the ink jet chambers is continuously under pressure and the catcher associated with the continuous ink jet system may be utilized until the ink jet is properly ejecting droplets. However, the demand ink jet system operates at substantially ambient pressures and must be properly primed to assure that a droplet of ink will be ejected from the jet upon demand when and only when such a droplet is desired.